I know that a lot of work is done right now on github primarily merging pull requests, branches and private Odoo forks into master(I suppose that this is somehow the v9 branch) but since there are no milestone issues for v9 no one can tell where will finish the need work to release the next version of Odoo. I know that Odoo s.a are working on a private fork in R & D but in my opinion it's a very bad use of community resources, Odoo developers are great but in the community you could find great developers too and the reason of develop and maintain an enterprise version(what is this? changes in usability and some few behaviors? a few differents modules?) doesn't seems to be a good reason to have the community away from the development of core modules and roadmap of the release. Could have the better internals of direction from Odoo point of view but for me it's not a very intelligent way of do this. Take an example:

Someone download an odoo_9.0alpha1.latest.tar.gz from nightly master, found some bugs or may have an another opinion of how something should be done, technically or functional.

Where should he will be report those issues?, Github? doesn't seems to have any issue activity, just acting like a forum, there is no referenced commits/pull requests/comments/responsible for the issues. How will he known that someone is working or not in those issues for he/she(of course) that decided to begin working on resolve what he found and make a pull request, how those pull request will known to be ok without a discusion of what need to be done? or who else is working on that? to join efforts or to not break something when another existing pull request get merged?. It's for a crazy person start right now to work on something complex and with a high level of efforts without this knowledge just for see their work in the trash when he discover that he miss the shot in what he though that was ok.

This are just ideas, but I'm sure that they are happening actually because of how Odoo S.A are managing things around the development of Odoo core and addons. I'm happy to contribute in every way I can to open sources projects but the contributions in Odoo seems to be restricted by Odoo S.A itself.

To answer your question about the release date: it will be released on 1 october 2015.You're correct that Odoo is working with private repo's / forks on Github and the reason behind is their new licensing system and how they will make a part of Odoo paid. As for the licensing, what will change and what will be paid.. I've made another post about this on the forums here so I'll quote from my original answer.

In version 9 we will see a rather big change in terms of licensing.Odoo V8 was licensed under AGPLv3 and this will now change to LGPLv3 in combination with OE.
So, what will this change involve? Odoo 9 changes to LGPLv3 and becomes the Odoo community edition. The LGPLv3 licensing will allow anybody to sell Odoo apps on the app store. Besides of the Odoo 9 community edition there will be a V9 Enterprise Edition. This is a pretty big game changer in Odoo 9 and directly stears Odoo from being fully open sourced to being partially open sourced and partially closed. The Enterprise Edition will contain a set of new apps on top of the Odoo community edition.
A good thing to know is that the Enterprise Edition will never be open-sourced and the code will only be available to official Odoo partners and Odoo itselfs. This also means that a non-official partner cannot sell the Enterprise Edition and thus an Odoo customer can only buy the Enterprise Version from Odoo or its partners. Another interesting fact is that the Enterprise Edition will contain full responsiveness! It will fully adapt itself to mobile, tablet, computer,.. and means that this will be the first Odoo version that is truely mobile useable.
If you would like to have access to these features you will need to buy the Enterprise version, which will be an additional 20€ per user per month.
The modules that we now know in Odoo 8 will remain available for anyone in V9, without any extra cost, and will always be publicly on Github. New apps that will be in the Enterprise contract are account_dashboard, account_check_print, web_mobile, project_forecast and probably a whole lot more that are not publicly discussed yet.
While this post covers the basic information and details it still misses a lot of information. There is still limited information available at the moment and this will keep expanding when we get towards the release of Odoo 9 (Q4 2015). You can view the official presentation about licensing from Olivier Dony here: https://www.odoo.com/slides/slide/open-source-licenses-196

When a user finds a problem or bug he can directly report it on Github (https://github.com/odoo/odoo/issues). When a user has a good idea to make something better or to extend Odoo he can create a pull request (https://github.com/odoo/odoo/pulls). I honestly agree with you about the fact that communication is bad honestly. A lot of those pull requests are ignored or not accepted because they do not follow some sort of rule and then I'm not even talking about those that create a pull request for a bug that is already fixed somewhere else.. The main problems here are that Odoo has bad documentation (which is slowly getting better) and that the communication is bad. The interaction with the community isn't good enough for programmers. I honestly have though about extending Odoo and creating new things but I simply haven't because I know they will be refused or ignored. Odoo has announced they will be putting more resources on Github so that issues and pull requests get handled faster though, which is great to hear!

At the moment communication and documentation are still rather bad but there has been quite some improvement already so I assume this is a question of time. Lets not forget that Odoo has grown quite hard the last years and I'm sure this brings plenty of resource problems. The licensing and partially developing behind closed doors is something a lot of people have already complained about and I'm sure it will stay a much talked about topic.

I'm afraid that Odoo is shooting into their own leg. For example, responsiveness is in fact the only accepted way by Google mobile-friendly rules and of course the backend side of the system should follow the same idea than the front-end.

Such a great boost that Odoo has had lately should not get split into widely distributed community efforts. We should work for the same goal but in this way the project starts to get forked. It's very easy to understand and respect that some modules can be paid ones but when it goes to the subscription level and there is a developer working to his client, he rather makes his own module to his customers than gets his client hooked with Odoo subscriptions. It is very confusing for the end-client to get invoicing from several directions and the feeling the open-source independence is damaged!

The community seems to be generally very confused at the moment. Developers are not knowing into which direction to put their efforts and if it is worth to work for Odoo when your donated time may end up benefitting the Enterprise version (it uses the same core). Great videos are made with new functions but then you need to filter them by guessing what you can get and what not without subscription. Imagine you have 10 users and you basically only would love to get the responsive UI parts: 12 x 200 euro = 2400 euro. You can develop a lot already with this one year budget for yourself but then the effort stays only inside your company, not for the community. I guess we can start expecting lot of different looking private Odoo systems!

I think the Odoo themes and apps sold at the moment are great since they do not restrict the further development but greatly accompany the community efforts.